What Is A Drainage Swale?

Drainage swales are shallow, landscaped drainage channels or depressions designed to manage surface water runoff around a property. This diverts it away from the property and prevents both flooding and soil erosion during heavy rainfall.

As a part of a wider Sustainable Drainage Systems (SuDS) plan, swales can reduce standing water, protect property foundations and improve the aesthetics of your garden. We all know how the intensity of rainfall here in the UK is increasing, which is why we need more effective water management in both rural areas as well as across urban developments.

This month at Express Drainage Surveys, as experts in professional surveys to identify drainage issues, we’re covering everything you need to know about swales. This will include how they work, signs that a swale is needed and when you should involve drainage experts such as ourselves.

What exactly is a drainage swale?

Swales are a part of SuDS in the UK because they help to naturally guide rainwater without negatively impacting the environment. A swale is different from a ditch because it is usually:

An engineered depression or channel
A grassed or vegetated space – to spread and soak up the water
A controlled gradient designed for infiltration and conveyance

A drainage swale is particularly effective for areas with hard surfaces that can increase the flow of rainwater, such as driveways, patios and roads. While commonly found on business parks or housing developments, they can be used in private gardens and sometimes make an attractive garden feature.

How does a drainage swale work?

There are several distinct ways in which a drainage swale works. Let’s take a look at the process and its various parts:

Collecting water: The main aim of a drainage swale is to collect rainfall and surface water as it makes its way naturally to the lowest point. The swale intercepts the runoff and guides it into the shallow channel.
Slowing the flow: Implementing a gentle gradient and some vegetation can slow down the movement of water. This can reduce erosion caused by fast-flowing water.
Promoting infiltration: Because of the slower movement of the water, there is more time for the ground to soak it up. Rainfall is then partially filtered by the soil beneath the ground, removing pollutants and improving groundwater quality.
Conveying excess water: Once the ground beneath is fully saturated, the swale can direct any excess water to an appropriate outlet, such as a soakaway, drainage ditch or permeable area.
Seasonal variation: While during heavy rainfall, the swale may fill and hold water to be absorbed or discharged, during dry periods, it is largely invisible and blends into the landscape.

The multiple functions of a swale are what make them so valuable in the fight against flooding and in the battle to secure more sustainable water management avenues.

Why swales are important for UK properties

Here in the UK, intense rainfall and extended periods of rain are becoming more common, which puts a lot of pressure on our existing drainage systems. Properties in affected areas will struggle with runoff due to compacted soil, increased paving and outdated drainage infrastructure.

A drainage swale is a practical, environmentally friendly option for domestic gardens, commercial sites and rural land alike.

The benefits for homeowners include:

A reduction in localised flooding, capturing water before it can reach homes
The prevention of waterlogging for lawns or soft landscaping areas
The protection of building foundations, directing water away from walls and basements
Enhanced garden designs, blending naturally with any chosen planting scheme

The benefits for public and commercial areas include:

A reduction in the pressure on public sewers, thereby lowering the risk of flooding during a storm
Compliance with SuDS requirements that are often mandated by planning authorities
Improved biodiversity, supporting wildlife through vegetated channels to make the area a nicer place in which to live or work

Signs you may need a drainage swale

If you’re a homeowner, you may not realise that you have a drainage issue unless you’re already experiencing the effects of water damage. A swale could be the right solution for you if you’ve noticed any of the following signs:

Standing water that sits on your lawn for hours or days after a downpour
Water pooling near your foundations, paving or walls
Soil erosion on sloped areas where water washes soil away
Moss-covered or boggy grass, indicating consistent damp conditions
Runoff flowing from a neighbour’s property, which then impacts yours
Driveway or path flooding, suggesting that your drainage is overwhelmed
Waterlogged flower beds where your plants struggle to take hold

If you find yourself facing these issues, you might find that a drainage survey could help to identify the cause. This can also help confirm whether a swale is a viable solution for your property.

The different types of drainage swales

Swales come in multiple forms, with each type suited to different soils, landscapes and drainage needs. To help you understand which design might work best for you, here are the common types simplified:

Dry swales: designed to only carry water during periods of heavy rain
Wet swales: designed to hold water for longer due to high water tables or impermeable soils
Vegetated swales: planted with grass, wildflowers or natural vegetation to support nature and improve pollution treatment
Swale and soakaways combinations: making use of the swale to control the flow, but implementing the storage capacity of a soakaway

How Express Drainage Surveys can help

Because we’re providers of advanced drainage surveys, using recorded images and evidential reports, we can provide information on any blockages, repairs or maintenance that your drainage system needs. As part of this, we can also identify if a swale is an appropriate measure to implement.

You can learn more about our wide variety of services to help protect your home or business via the following pages:

Contact us today to book a drain survey and to discuss the long-term health of your drainage system if you’re wondering whether a swale is the right solution to the issues you’re experiencing.